MOFs fiber composite material as well as preparation method and application thereof

Abstract

The invention provides an MOFs fiber composite material and a preparation method and application thereof, and belongs to the field of fiber composite materials. The composite material takes polyacrylonitrile as a matrix, MOFs (Metal-Organic Frameworks) are cross-linked and compounded by adopting a mercaptoacetic acid locked imine reaction, and the structure of the composite material is shown as a formula 1. The MOFs and polyacrylonitrile are firmly compounded through chemical crosslinking, the problem that the MOFs are not easy to form and separate is solved, adsorption sites containing N and S atoms are introduced into the MOFs fiber composite material through simple thioglycolic acid imine locking reaction, and the adsorption capacity and selectivity of the material to Pd (II) are improved.

Description

Technical Field

[0001] The present invention belongs to the field of fiber composite materials, and particularly relates to a MOFs fiber composite material, a preparation method thereof and an application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) are a class of porous crystalline materials with a periodic network structure formed by the self-assembly of metal ions and organic ligands through coordination, usually having a very high specific surface area and an easily controllable structure. However, existing MOFs materials are mostly brittle powder forms, which are not easy to process and shape, and are difficult to separate in the liquid phase. Summary of the Invention

[0003] The purpose of the present invention is to provide a composite material of polyacrylonitrile and MOFs, a preparation method thereof and an application thereof. The composite material combines the characteristics of easy processing and good flexibility of polyacrylonitrile and high specific surface area and large adsorption capacity of MOFs, and is suitable for the efficient adsorption and separation of Pd(II).

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] The present invention first provides a composite material of polyacrylonitrile and MOFs. The composite material uses polyacrylonitrile as the matrix and crosslinks and composites MOFs by using the mercaptoacetic acid-locked imine reaction. Its structure is as shown in Formula 1:

[0006]

[0007] In Formula 1, n = 1-4.

[0008] Preferably, the MOFs include the UiO series or the MIL series.

[0009] The present invention also provides a preparation method of the above composite material, including the following steps:

[0010] Step 1: Modify polyacrylonitrile with a lithium aluminum hydride ether solution or a polyamine solution to obtain modified polyacrylonitrile;

[0011] Step 2: Dissolve a metal salt in a solvent, then add the modified polyacrylonitrile obtained in Step 1 for impregnation, and dry to obtain salt-impregnated polyacrylonitrile;

[0012] Step 3: Dissolve an amino-containing organic ligand in a solvent, then add glacial acetic acid and the salt-impregnated polyacrylonitrile obtained in Step 2, mix evenly, transfer to an autoclave for reaction. After cooling to room temperature, filter out the material, wash it, and then add a dialdehyde, mercaptoacetic acid and a solvent to stir and react to obtain a composite material of polyacrylonitrile and MOFs.

[0013] Preferably, the modification in Step 1 is specifically as follows: polyacrylonitrile is put into a lithium aluminum hydride ether solution and stirred, or polyacrylonitrile is immersed in a polyamine solution and heated under reflux to obtain modified polyacrylonitrile.

[0014] Preferably, the ether in the lithium aluminum hydride ether solution is one or a mixture of two of diethyl ether and propyl ether.

[0015] Preferably, the polyamine is selected from one of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,3 - propanediamine or polyethyleneimine.

[0016] Preferably, the stirring time is 6 - 24 h, and the heating reflux time is 2 - 12 h.

[0017] Preferably, the metal salt is one of zirconium chloride, hafnium chloride, chromium nitrate (nonahydrate), iron chloride (hexahydrate), aluminum nitrate (nonahydrate);

[0018] The amino - containing organic ligand is one of 2 - aminoterephthalic acid and 2 - amino - 4,4'-biphenyldicarboxylic acid;

[0019] The dialdehyde is one of malondialdehyde, succinaldehyde, glutaraldehyde or adipic dialdehyde;

[0020] The solvent is one or a mixture of two of water and DMF.

[0021] Preferably, in Step 3, the reaction temperature in the autoclave is 100 - 180 °C, and the reaction time is 12 - 48 hours.

[0022] The present invention also provides the application of the above composite material in the separation of Pd(II).

[0023] Advantages of the present invention

[0024] 1. The synthesis of the composite material provided by the present invention has simple operation and easily available raw materials, which is beneficial to large - scale production.

[0025] 2. The present invention firmly composites MOFs with polyacrylonitrile through chemical cross - linking, solving the problems that MOFs are not easy to form and difficult to separate.

[0026] 3. The present invention introduces N - and S - containing adsorption sites into the MOFs fiber composite material through a simple mercaptoacetic acid - locked imine reaction, improving the adsorption capacity and selectivity of the material for Pd(II). Description of the drawings

[0027] Figure 1 It is the infrared spectrogram of the modified polyacrylonitrile prepared in Example 1 of the present invention. Detailed embodiments

[0028] The present invention first provides a composite material of polyacrylonitrile and MOFs. The composite material uses polyacrylonitrile as the matrix and cross-links and composes MOFs by using mercaptoacetic acid to lock the imine reaction. Its structure is shown in Formula 1:

[0029]

[0030] According to the present invention, the MOFs preferably include the UiO series or the MIL series.

[0031] The present invention also provides a preparation method of the above composite material, including the following steps:

[0032] Step 1: Modify polyacrylonitrile with lithium aluminum hydride ether solution or polyamine solution. The modification is specifically preferably as follows: under nitrogen protection, mix lithium aluminum hydride and ether solution, and then add polyacrylonitrile and stir. The stirring time is preferably 6 - 24 h, more preferably 12 h, to obtain modified polyacrylonitrile P-1; the ether solution is preferably one or a mixture of two of diethyl ether and propyl ether. The mass ratio of polyacrylonitrile to lithium aluminum hydride is preferably 1:0.5 - 2, and the mass ratio of lithium aluminum hydride (g) to the volume of ether solution (mL) is preferably 0.5 - 2:80 - 200;

[0033] Or immerse polyacrylonitrile in polyamine solution, heat under reflux. The heat reflux time is preferably 2 - 12 h, more preferably 6 h, wash to neutrality, and dry under vacuum to obtain modified polyacrylonitrile P-2; the polyamine is preferably selected from one of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,3 - propanediamine, or polyethyleneimine. The mass ratio of polyacrylonitrile (g) to the volume of polyamine (mL) is 1 - 5:40 - 200;

[0034] The polyacrylonitrile is in the form of fibers or a fabric composed of fibers;

[0035] Step 2: Dissolve the metal salt in a solvent and then add the modified polyacrylonitrile obtained in Step 1 for impregnation. The impregnation time is preferably 10 minutes, and preferably dry under vacuum at 130 °C for 2 hours to obtain salt-impregnated polyacrylonitrile; the metal salt is one of zirconium chloride, hafnium chloride, chromium nitrate (nonahydrate), iron chloride (hexahydrate), aluminum nitrate (nonahydrate); the solvent is one or a mixture of two of water and DMF; the mass ratio of the metal salt to the modified polyacrylonitrile is preferably 0.5 - 2:1;

[0036] Step 3: Dissolve the amino-containing organic ligand in a solvent, then add glacial acetic acid and the salt-impregnated polyacrylonitrile obtained in Step 2. The solvent is one or a mixture of two of water and DMF; after mixing evenly, transfer it to an autoclave for reaction. The reaction temperature is preferably 120 °C, and the reaction time is preferably 24 hours. After cooling to room temperature, filter out the material, wash it, and then add dialdehyde, mercaptoacetic acid and the solvent and stir for reaction. The reaction temperature is preferably room temperature, and the reaction time is preferably 4 hours to obtain a composite material of polyacrylonitrile and MOFs.

[0037] The amino-containing organic ligand is preferably one of 2-aminoterephthalic acid and 2-amino-4,4'-biphenyldicarboxylic acid; the dialdehyde is preferably one of malonaldehyde, succinaldehyde, glutaraldehyde or adipaldehyde; the solvent is one or a mixture of two of water and DMF; the molar ratio of the amino-containing organic ligand, glacial acetic acid, dialdehyde, and mercaptoacetic acid is preferably 5-20:10-40:1-10:1-5; the mass g of the salt-impregnated polyacrylonitrile: the volume mL of the solvent is 0.5:10-30.

[0038] The present invention also provides the application of the above composite material in the separation of Pd(II).

[0039] The following further describes the present invention in detail with specific examples. All raw materials involved in the examples are obtained commercially.

[0040] Example 1

[0041] Step 1: Put 120 mL of dry ether and 1.5 g of lithium aluminum hydride into a 250 mL round-bottom flask, mix evenly, add 1.5 g of polyacrylonitrile, and stir for 12 hours under nitrogen protection. Filter and wash with deionized water, and then vacuum dry for 4 hours to obtain modified polyacrylonitrile (P-1).

[0042] Step 2: Dissolve 0.7 g of zirconium chloride in 50 mL of a mixed solvent (composed of 25 mL of water and 25 mL of DMF) and add 1.0 g of P-1 for impregnation for 10 minutes. After taking out the material, place it in a vacuum dryer at 130 °C for 2 hours to obtain salt-impregnated P-1;

[0043] Step 3: Dissolve 0.7 g of 2-aminoterephthalic acid in 20 mL of a mixed solvent (composed of 10 mL of water and 10 mL of DMF), then take 1.2 mL of glacial acetic acid, mix it evenly with the salt-impregnated P-1, and transfer it to an autoclave for reaction at 120 °C for 24 hours. After cooling to room temperature, add 0.5 g of the filtered material, 0.6 mL of glutaraldehyde and 0.3 mL of mercaptoacetic acid to 25 mL of a mixed solvent (composed of 12.5 mL of water and 12.5 mL of DMF), and stir for reaction at room temperature for 4 hours to obtain a polyacrylonitrile-MOFs composite material (PM-1).

[0044] The infrared spectra of PM-1 and the polyacrylonitrile matrix are as Figure 1 shown. The solid line is for PM-1 and the dashed line is for polyacrylonitrile. At 2241 cm-1, the absorption peak of C≡N significantly weakens, proving that the cyano groups on the polyacrylonitrile have indeed undergone transformation; a characteristic peak of the bending vibration of the C-S-C bond appears at 1427 cm-1, proving the successful compounding of the materials.

[0045] Example 2

[0046] The operation steps are the same as those in Example 1, except that when preparing the composite material, 1.2 g of chromium nitrate (nonahydrate) is used as the metal salt to replace 0.7 g of zirconium chloride, and the temperature for heating the autoclave in Step 3 is adjusted to 150 °C. The obtained composite adsorption material is labeled as PM-2.

[0047] Example 3

[0048] The operation steps are the same as those in Example 1, except that when preparing the composite material, 0.7 mL of adipic aldehyde is used to replace 0.6 mL of glutaraldehyde. The obtained composite adsorption material is labeled as PM-3.

[0049] Example 4

[0050] Step 1: Mix 1.0 g of polyacrylonitrile with 40 mL of a 70% triethylenetetramine solution and stir at 120 °C for 6 hours. Rinse the material with cold water and hot water repeatedly until the filtrate is neutral. Dry the material in vacuum at 90 °C to obtain modified polyacrylonitrile (P-2).

[0051] Step 2: Dissolve 0.7 g of zirconium chloride in 50 mL of a mixed solvent (composed of 25 mL of water and 25 mL of DMF), add 1.0 g of P-2, and impregnate for 10 minutes. After taking out the material, dry it in vacuum at 130 °C for 2 hours to obtain salt-impregnated P-2;

[0052] Step 3: Dissolve 0.7 g of 2-aminoterephthalic acid in 20 mL of a mixed solvent (composed of 10 mL of water and 10 mL of DMF), then take 1.2 mL of glacial acetic acid, mix it evenly with the salt-impregnated P-2, transfer it to an autoclave, and react at 120 °C for 24 hours. After cooling to room temperature, add 0.5 g of the filtered material, 0.6 mL of glutaraldehyde, and 0.3 mL of mercaptoacetic acid to 25 mL of a mixed solvent (composed of 12.5 mL of water and 12.5 mL of DMF), and stir and react at room temperature for 4 hours to obtain a polyacrylonitrile-MOFs composite material (PM-4).

[0053] Example 5

[0054] The operation steps are the same as those in Example 4, except that when preparing the composite material, 1.2 g of chromium nitrate (nonahydrate) is used as the metal salt to replace 0.7 g of zirconium chloride, and the temperature for heating the autoclave in Step 3 is adjusted to 150 °C. The obtained composite adsorbent is labeled as PM-5.

[0055] Example 6

[0056] The operation steps are the same as those in Example 4, except that when preparing the composite material, 0.7 mL of adipic aldehyde is used to replace 0.6 mL of glutaraldehyde. The obtained composite adsorbent is labeled as PM-6.

[0057] Weigh 1.0 g of the composite adsorbents prepared in Examples 1 to 6, and separately load them into dynamic adsorption columns (diameter 6 mm, height 80 mm), and conduct dynamic adsorption experiments with Pd(II)-containing wastewater with an initial concentration of 100 mg / L. The adsorption effects of the composite materials obtained in Examples 1 to 6 are shown in Table 1 below.

[0058] Table 1 Adsorption effects of polyacrylonitrile-MOFs composite materials

[0059]

[0060] As can be seen from Table 1, the above six polyacrylonitrile-MOFs composite materials all have excellent adsorption effects on Pd(II) ions. Among them, the materials obtained by compounding polyamine-modified polyacrylonitrile with MOFs (Examples 4 to 6) have better adsorption performance.

[0061] The above content is only the preferred embodiments of the present invention, and those skilled in the relevant art can make certain modifications to the present invention within the scope of their knowledge. If the modified content is within the scope of the claims of the present invention and its equivalent technologies, it should also be within the protection scope of the present invention.

Claims

1. A composite material of polyacrylonitrile and MOFs, characterized in that, The composite material uses polyacrylonitrile as the matrix, and crosslinks and composites MOFs by using the mercaptoacetic acid-locked imine reaction. Its structure is shown in Formula 1: In Formula 1, n = 1 - 4.

2. The composite material of polyacrylonitrile and MOFs according to claim 1, characterized in that, The MOFs include the UiO series or the MIL series.

3. The preparation method of a composite material of polyacrylonitrile and MOFs according to claim 1, characterized in that, It includes the following steps: Step 1: Modify polyacrylonitrile with a lithium aluminum hydride ether solution or a polyamine solution to obtain modified polyacrylonitrile; Step 2: Dissolve the metal salt in a solvent, then add the modified polyacrylonitrile obtained in Step 1 for impregnation, and dry to obtain salt-impregnated polyacrylonitrile; Step 3: Dissolve the amino-containing organic ligand in a solvent, then add glacial acetic acid and the salt-impregnated polyacrylonitrile obtained in Step 2, mix evenly, transfer to an autoclave for reaction. After cooling to room temperature, filter out the material, wash it, and then add a dialdehyde, mercaptoacetic acid and a solvent and stir for reaction to obtain a composite material of polyacrylonitrile and MOFs.

4. The preparation method of a composite material of polyacrylonitrile and MOFs according to claim 3, characterized in that, The modification in Step 1 is specifically: put polyacrylonitrile into a lithium aluminum hydride ether solution and stir, or immerse polyacrylonitrile in a polyamine solution and heat under reflux to obtain modified polyacrylonitrile.

5. The preparation method of a composite material of polyacrylonitrile and MOFs according to claim 4, characterized in that, The ether in the lithium aluminum hydride ether solution is one or a mixture of two of diethyl ether and propyl ether.

6. The preparation method of a composite material of polyacrylonitrile and MOFs according to claim 4, characterized in that, The polyamine is selected from one of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,3-propanediamine or polyethyleneimine.

7. The preparation method of a composite material of polyacrylonitrile and MOFs according to claim 4, characterized in that, The stirring time is 6 - 24 h, and the heating reflux time is 2 - 12 h.

8. The preparation method of a composite material of polyacrylonitrile and MOFs according to claim 3, characterized in that, The metal salt is one of zirconium chloride, hafnium chloride, chromium nitrate (nonahydrate), iron chloride (hexahydrate), aluminum nitrate (nonahydrate); The amino-containing organic ligand is one of 2-aminoterephthalic acid and 2-amino-4,4'-biphenyldicarboxylic acid; The dialdehyde is one of malondialdehyde, succinaldehyde, glutaraldehyde or adipaldehyde; The solvent is one or a mixture of two of water and DMF.

9. The preparation method of a composite material of polyacrylonitrile and MOFs according to claim 3, characterized in that, The reaction temperature in the autoclave in Step 3 is 100 - 180 °C, and the reaction time is 12 - 48 hours.

10. Application of the composite material of polyacrylonitrile and MOFs according to Claim 1 in separating Pd(II).

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